The present invention relates generally to intrinsic injection molding gates and a method of overmolding cordage. More specifically, this disclosure relates to a mold configuration wherein intrinsic injection molding gates are formed between the injection mold and the cordage to be overmolded.
Some commonly found examples of injection molding over cordage, include items such as dog retrieving dummies, boat docking buoys, dock lines and water ski ropes. When the overmolded portion is in the running length of the cordage, it is relatively easy to stabilize the cordage under tension and keep the overmolded portion properly located in the overmolded feature. However, for overmolding to be successful when the feature is on the end of the cordage, the overmolded portion must be thick enough to cover any included mechanical keys, knots or to simply cover the cordage if any side to side movement of the overmolded end occurs. Typically, the thickness of the overmold, measuring from the centerline of the overmold to the thinnest outside surface, must be equal to, or greater than, the length of cordage desired to be overmolded.
There are other common applications where overmolding may be desirable but is not presently used. Elastomeric and plastic parts are routinely adhesively attached to a section of cordage and some metal or plastic parts are mechanically connected. These methods are used to create, commonly known in the art, eyeglass retainers, bracelets, necklaces and identification lanyards. However, each of these methods requires multiple manufacturing and assembly steps. For example, in order to form an eyeglass retainer using a section of cordage with elastomeric connectors; cordage must be cut to length, injection mold a pair of elastomeric connectors, stage cordage, stage connectors, select cordage, manually apply adhesive to each end the cordage, select connectors, manually insert each end of the cordage into sockets in the elastomeric connectors, remove excess adhesive and place in drying area to allow for adhesive cure prior to packaging. Some of the issues and shortcomings related to this method of manual assembly include, accuracy of assembly, appearance of finished product, durability of the adhesive connection, messiness of the adhesive, exposure to the adhesive fumes, flammability of most adhesives, workplace ventilation requirements, staging of parts, rehandling of parts, time of production, task redundancy, worker fatigue and high labor costs. Issues with mechanically connected parts may include, accuracy of assembly, appearance of the finished product, durability of the assembly, staging of parts, rehandling of parts, time of production, machinery requirements, task redundancy, worker fatigue, risk of injury from machinery, risk of injury from repetitive task, and high labor costs.
It is generally accepted in industry that when a high volume of similar parts or products are required, mechanical assembly is preferable, and allows the manufacturer to provide a consistent, high quality product, at a reduced cost. However, when the product requires supple and relatively thin cordage and a plastic or elastomeric part having a thin profile, again, in items such as, eyeglass retainers, necklaces, bracelets or lanyards, the conventional methods of injection molding are not suited to provide an acceptable product. It has been found that when a supple thin section of cordage is inserted into a conventional mold body and elastomeric material is injected around the cordage, the initial surge of viscous material through the mold injection gate forces the cordage against the opposing wall of the mold body and the finished product will have either an undesirably thin overmolded section or the cordage will be exposed through overmolded material on the side opposite the injection gate.
Therefore, there is a need in the industry for an injection mold and method of use that allows a user to overmold elastomeric or plastic material over an end section of cordage and, more specifically, allow a user to overmold elastomeric or plastic material over an end section of supple thin cordage.